1. Field of the Invention
This invention is concerned with a spacer for use in spacing a disc of a track-adjustable wheel from attachment means of a rim of the wheel to which the disc is bolted.
Track-adjustable wheels are frequently utilised on agricultural tractors and other vehicles to enable the track to be adjusted to suit particular requirements. Such wheels comprise a rim on which a tire is mounted, the rim having attachment means, normally in the form of lugs, welded thereto, and a disc which is bolted to the attachment means of the rim and is also secured to a hub of the tractor. The disc is bowed so that two positions of adjustment can be achieved by securing the disc one way round or the other. The disc can also be attached to either side of the attachment means so that the adjustment possibilities reaches four. Furthermore, the rim itself can be reversed doubling the possibilities to make a total of eight possible adjustment positions. In a conventional wheel, the lugs are of sufficient extent transversely of the wheel that the attachment of the disc to one side or the other thereof gives a considerable variation in the track.
In the specification of British Patent No. 2 167 717, a track-adjustable wheel is described in which, instead of lugs, the attachment means of the rim comprises a ring welded continuously to the rim around an outer circumference of the ring. This ring is planar and relatively thin so that only a small track-adjustment can be achieved by altering the side to which the disc is bolted. To provide a greater variation, spacers are introduced between the ring and the disc, the spacers each having a bolt-receiving passage therethrough and a first bearing surface which extends around a mouth at one end of the passage and a second bearing surface which extends around a mouth at the opposite end of the passage. One of these bearing surfaces rests against the ring while the other rests against the disc. In one way of assembling the track-adjustable wheel described in the above-mentioned British Patent Specification No. 2 167 717, the rim is placed horizontally, the spacers are positioned on the upper surface of the ring so that the bolt-receiving passage of each spacer is aligned with a bolt-receiving passage in the ring, the disc is positioned on top of the spacers so that bolt-receiving passages in the disc are aligned with the bolt-receiving passages of the spacers, and bolts are inserted so that each extends through a bolt receiving passage in the ring, a spacer and the disc. Nuts are then tightened on to the bolts and the wheel can then be mounted on the hub of a tractor. However, because in some cases there is only a small clearance between the rim and the bolt-receiving passage of the ring, there being a weld present at the junction of the ring with the rim, and because of the necessity to provide the spacer with bearing surfaces of sufficient size to carry the load required, it is necessary that the spacers are not axi-symmetric so that they need to be in one of a number of specific orientations when the bolts are tightened. However, it is found that the orientation of the spacers is liable to alter during the above-described assembly process with a consequent danger that when the bolts are tightened the spacers may not be correctly seated against the ring and the disc. For example, a spacer may foul the weld between the ring and the rim so that although the bolts may be tight, the spacing between the ring and the disc may not be constant around the wheel.
It is an object of the present invention to provide a spacer for use in spacing a disc of a track-adjustable wheel from attachment means of a rim of the wheel to which the disc is bolted, the spacer avoiding the possibility of the orientation of the spacer altering during the assembly of the wheel.